45 Degrees of Tone: The JTM45 Roundup

Nearly 50 years
since its creation,
the Marshall
JTM45 remains both a relevant
and near-perfect example
of what a
great rock ‘n’ roll tube amp
should be.

It was originally built around the design of
one of Jim Marshall’s favorites, the Fender
Bassman; like the Bassman, the JTM45 was
actually a fantastic guitar amp. Because
of its consistent popularity, Marshall has
offered a reissue version of the head—
more than 20 years after production of
the original JTM45 ceased. While the
reissue is built with modern components
and assembly techniques, it retains much
of the tone, responsiveness and character
of the original, hand-wired versions of
the early days. No wonder builders today
still carry on the tradition of the JTM45,
and guitarists continue to seek out the
pure simplicity and touch response of this
tone machine. To celebrate the JTM45, I
got together with my Sunday afternoon
amp group, after contacting a handful of
respected amp builders who sent us their
versions of the amp. We fired them all up
alongside an original and a reissue JTM45
to take a listen—and to enjoy one of the
best amps ever designed.

About the Authors
About 5 years ago, while playing a 9/11 benefit
show, I had the good fortune to meet two people
who would not only profoundly impact my life
with tube amps, but would become lifelong
friends. John Rossi and Tony Burns were there
that day; Tony, a killer player and a regular on
the Tempe/Phoenix music scene, and Johnny, his
friend and amp tech, making sure Tony’s amps
were running well in 115 degree heat at the
outdoor amphitheater. When I saw Tony’s wall of
Marshalls next to my backline of Marshalls, it was
an instant conversation starter.

We spent time between sets that day discussing
the various finer points of our amps and gawking
at each other’s rigs. The show went great but my
’67 Super P.A. felt a bit stiff, and wasn’t reacting
in the most flattering way. This incident proved to
be the catalyst, as Johnny was an underground
semi-retired tech and ultra-fanatic Marshall enthusiast,
and he had some ideas that he wanted to try
out. He invited me over the following Sunday to
check out the amp, and to experiment with various
preamp and power amp tubes while BBQ-ing and
having a beer. Tony was there, and it became clear
that we all had a deep respect for these amps;
rather than modify them, we wanted to bring
them back to their former glory. After five years,
and dozens of hacked-up Marshalls coming back
from the dead, here we are. Over that time we’ve
learned more about these amazing amps than any
of us ever anticipated, and we’ve have had a blast
in the process. I have no doubt in my mind, based
on my readings of the various amp forums, that
there are plenty of groups just like us all over the
world doing the same thing.

The Lineup
The lineup consisted of our own 1965 original and 1990 reissue heads, two
MetroAmp JTM45s (a kit version as well
as the GPM 45), a Germino Classic 45, a
Wallace Amplification BKW45 and Mojave Ampworks’ new Special Edition Plexi 45
head. After searching through our collection
of cabinets, we settled on both
an eighties Marshall JCM800 4x12 with
blackback 25s, and a Mojave 2x12 cab with
1963-era Celestion Alnico Blues. It may
sound strange that there were no pinstripe
or basketweave cabs used for the roundup,
but that wasn’t for lack of trying. Among all
the members of the amp group, we actually
have a pinstripe, a basketweave and a variety
of Marshall 4x12s, but for some reason
we always come back to the early-eighties
JCM 800 cab with blackback 25s.

That particular cab has more clarity, tone
and authority than any other, and it remains
our favorite in the bunch—despite the cool
factor of the older cabs. The 2x12 with
Blues was a natural choice, as that flavor
shares similarities with the mid-sixties
Marshall cabs and is also a popular speaker
configuration for Bluesbreaker combos. The
guitars we used were our standard array
of Les Pauls from the ‘70s, ‘80s and 2000s,
as well as a newer 2008 Fender Strat and
two early-seventies Strats. With everything
in the room (it was quite a sight!) we were
ready to begin.

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